The present invention relates to an inkjet printer including a plurality of fixed printheads. The present invention also relates to the printing of labels, receipts, bar code labels, tags, airline tickets and the like.
Inkjet printers are commonly used for printing receipts for point-of-sale transactions at supermarkets, retail stores and other businesses. A typical fixed printhead inkjet printer includes an array of printheads that are fixed relative to a print medium path. The printheads are staggered to achieve full printing width. For example, five printheads 10a-10e may be staggered as shown in FIG. 1. During printing, a print medium 12 is pulled off a supply roll and advanced in a forward direction along a flow axis. This forward direction is indicated by a first arrow F.
As the print medium 12 passes beneath the printheads 10a-10e, the printheads 10a-10e lay down swaths of ink dots on the print medium 12. After the printing has finished, the printed portion is advanced out of the printer and separated from the remainder of the print medium.
The print medium remaining in the printer has a large blank portion that begins at the first printhead 10a and terminates at a xe2x80x9cleading edgexe2x80x9d L. To avoid wasting print medium, the leading edge L is retraced back into the printer, near the first printhead 10a (the direction of retracing is indicated by a second arrow R). The retracing allows the printing of the next printout to begin near the leading edge L of the print medium 12.
When retracing the print medium, the leading edge should not be allowed to flap around. A vacuum hold down mechanism is typically used to control the leading edge as the print medium is being retraced. However, the vacuum hold down mechanism increases the complexity of the print medium path assembly.
Retracing the print medium also takes time, especially when the print medium is retraced over long distances. The retracing slows down the printing of labels, receipts, and the like.
Pulling the print medium back onto the supply roll during retracing can cause problems for the print medium back tensioning system of the printer. Edges of the print medium can also catch during retracing. Thus, the retracing can reduce handling reliability of the print medium.
According to one aspect of the present invention, a printer includes a plurality of fixed printheads; a print medium path; and a transfer roller for transferring ink from the printheads to a transfer zone on the print medium path. Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.